Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/36—Compounds of titanium
  • C09C1/3607—Titanium dioxide
  • C09C1/3653—Treatment with inorganic compounds
  • C09C1/3661—Coating
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31844—Of natural gum, rosin, natural oil or lac
  • Y10T428/31848—Next to cellulosic
  • Y10T428/31851—Natural oil

Definitions

• the field of the invention is the field of methods for the surface treatment of titanium dioxide pigments to produce a titanium dioxide pigment with high greying resistance and high hiding power, and its use in the production of decorative laminating paper.
• decorative laminating papers permits the production of decorative surfaces, where the decorative laminating paper serves not only as facing paper for unattractive wood material surfaces, but also as a carrier for the synthetic resin.
• the requirements imposed on decorative laminating paper include, for example, hiding power (opacity), light-fastness (greying resistance), colour-fastness, wet strength, impregnability and printability.
• a pigment based on titanium dioxide is eminently suitable for achieving the necessary opacity of the decorative laminating paper.
• a titanium dioxide pigment or a titanium dioxide pigment suspension is mixed with a fibre suspension during paper production.
• the interactions between the individual components (fibres, pigment, water) contribute to formation of the paper sheet and determine the retention of the pigment.
• retention refers to the retention of all inorganic substances in the paper during production.
• auxiliaries and additives are generally also used. These may affect the mechanisms of interaction between the fibres, the pigment and the water.
• titanium dioxide is photochemically active. When exposed to UV radiation in the presence of moisture, decorative laminating paper pigmented with titanium dioxide displays increasing greying. To avoid this problem, the surface of the pigments is treated with various substances, for instance with Al 2 O 3 aquate and a colourless metal phosphate (U.S. Pat. No. 3,926,660), with zinc phosphate (U.S. Pat. No. 5,114,486), with cerium phosphate and aluminium phosphate (GB 2 042 573), or only with aluminium phosphate (EP 0 753 546 A2).
• DE 15 92 873 describes a method for improving the light-fastness of pigments, where calcination at 600° C. is performed following coating with magnesium silicate.
• TiO 2 pigments with improved retention properties having a cores coated with consecutive layers of aluminium oxide phosphate, aluminium oxide and magnesium oxide, are presented in EP 0 713 904 B1, U.S. Pat. No. 5,665,466 and U.S. Pat. No. 5,942,281.
• the object of the present invention is to offer a method capable of producing pigments with high hiding power and simultaneously high greying resistance for use in decorative laminating papers.
• the object of the invention is, therefore, a method for the surface treatment of titanium dioxide pigments that results in pigments with high hiding power and high retention with simultaneously high greying resistance, as well as a pigment with these properties and the use of this pigment in the production of decorative laminating paper.
• the surface treatment process is based on TiO 2 base material, preferably produced by the chloride process.
• TiO 2 base material refers to the raw TiO 2 pigment prior to post-treatment.
• the base material can first be milled, for example in a wet-milling process. A dispersant is preferably added during wet-milling.
• the milled base material is used to prepare an aqueous suspension. This suspension can be basic or acidic and is preferably basic with a pH value of 9 to 11.
• the method is performed at a temperature of less than 70° C., preferably at 55 to 65° C.
• a phosphorus compound is added to the suspension in a quantity of 0.4 to 6.0% by weight, preferably 1.0 to 4.0% by weight, calculated as P 2 O 5 , referred to TiO 2 base material. Particularly good results are obtained with P 2 O 5 contents of 1.6 to 2.8% by weight, referred to the base material.
• Other suitable phosphorus compounds are preferably inorganic phosphorus compounds, such as alkali phosphates, ammonium phosphate, polyphosphates, phosphoric acid or, where appropriate, mixtures of these compounds. Other phosphorus compounds can, however, also be used.
• a titanium compound is added, e.g. titanyl sulphate, titanyl chloride or another hydrolysable titanium compound, or mixtures of these compounds.
• the quantity of titanium compound added is 0.1 to 3.0% by weight, preferably 0.1 to 1.5% by weight, and particularly 0.1 to 1.0% by weight, calculated as Ti O 2 referred to TiO 2 base material in the suspension.
• an aluminium compound of acidic or basic character is preferably subsequently added to the suspension.
• an acidic aluminium compound is aluminium sulphate, although this is not to be taken as a restriction.
• Suitable alkaline aluminium compounds include sodium aluminate, alkaline aluminium chloride, alkaline aluminium nitrate or other alkaline aluminium salts, or mixtures of these compounds.
• the suspension will customarily be stirred for about 30 minutes following each addition, in order to achieve homogenisation. It is, however, also possible to add the titanium compound and the aluminium compound simultaneously.
• an acid or a base, or a second aluminium compound is added in parallel with the aluminium compound, in order to maintain a constant pH value in the range from 2 to 10, preferably in the range from 4 to 9 and particularly in the range from 6 to 8.
• the pH value is controlled by the balanced, parallel addition of sodium aluminate and HCl.
• a further procedure consists in keeping the pH value constant by means of the controlled addition of aluminium sulphate and sodium aluminate.
• the suspension is subsequently adjusted to a pH value of 8 to 10, preferably 8.5 to 9.5.
• a person skilled in the art adjusts the pH value in the customary manner with the help of appropriate acidic or alkaline compounds.
• the alkalis used for this purpose include, for example, alkaline aluminium salts, such as sodium aluminate, alkaline aluminium chloride or alkaline aluminium nitrate, or bases, such as sodium hydroxide solution or ammonia, or a combination of these alkalis.
• the total quantity of aluminium added to the suspension by way of the various aluminium compounds is 2.0 to 7.5% by weight, preferably 3.5 to 7.5% by weight, calculated as A 2 O 3 , referred to TiO 2 base material.
• a magnesium compound 0.1 to 1% by weight, preferably 0.2 to 0.5% by weight, of a magnesium compound is then added, calculated as MgO and referred to TiO 2 base material.
• Suitable for use as the magnesium compound are water-soluble magnesium salts, such as magnesium sulphate, magnesium chloride and other magnesium salts, as well as mixtures of these compounds.
• the pH value should be maintained at 8 to 10, preferably at 8.5 to 9.5, and most preferably approximately 8 with the help of appropriate alkaline media, if necessary.
• the post-treated TiO 2 pigment is subsequently separated from the suspension by filtration, and the resultant filter cake is washed.
• the pigment can additionally be treated with nitrate at a concentration of up to 1.0% by weight in the finished pigment.
• the final pH value of the pigment may be set by adding a suitable pH modifying substance such as an acid, a base, an acid salt, or a basic salt, or a combination of suitable substances.
• the pH value is controlled by means of the degree of acidity and the added quantity of the substance.
• all compounds may be used which do not impair the optical pigment properties, which are temperature resistant during the final pigment drying or pigment milling and which can be added to the filter paste, into the dryer or during steam jet milling.
• acids like sulphuric acid, nitric acid, hydrochloric acid or citric acid or acidic salts like chlorides, sulfates or the like are suitable if they comply to the conditions specified.
• Nitrate compounds are particularly suitable. By utilizing sodium nitrate the final pH value comes to more than 9. Yet, the decrease of the pH value can be achieved by the use of acidic nitrate compounds or a combination of acidic and non-acidic nitrate compounds as for instance aluminium nitrate, a combination of aluminium nitrate and sodium nitrate, a combination of aluminium nitrate and nitric acid and so forth.
• aluminium nitrate in a quantity of 0.4% by weight calculated as NO3 in the filter paste results in a lowered final pH value of from 7.5 to 8.5, preferably approximately 8.
• the pigment produced according to this method displays improved hiding power and improved greying resistance in the laminate, as well as good retention, and is outstandingly suitable for use in decorative laminating paper.
• the acidic suspension After stirring for 30 minutes, the acidic suspension is set to a pH value of 9.0 with the help of an alkaline sodium aluminate solution in a quantity of 3.7% by weight, calculated as Al 2 O 3 . The solution is added over a period of 40 minutes. After stirring for 30 minutes, 0.5% by weight MgO in the form of a magnesium sulphate solution is added. After further stirring for 30 minutes the suspension is set to a pH value of 9 with NaOH.
• the post-treated TiO 2 suspension is filtered and washed.
• the washed filter paste is dried in a spray drier and subsequently steammilled.
• the pigment is produced in a manner comparable to that described in Example 1, except that titanyl sulphate and magnesium sulphate are not components of the post-treatment.
• 2.4% by weight P 2 O 5 in the form of disodium hydrogenphosphate solution is added to the sand-milled TiO 2 suspension (400 g/l TiO 2 ), which has a temperature of 60° C. and a pH value of 10.
• 3.0% by weight Al 2 O 3 is mixed into the suspension in the form of acidic aluminium sulphate solution.
• the acidic suspension is set to a pH value of 7.2 with the help of an alkaline sodium aluminate solution in a quantity of 3.4% by weight, calculated as Al 2 O 3 .
• the further processing steps (filtration, washing, nitrate treatment, drying, milling) are the same as in Example 1.
• the titanium dioxide pigments produced as described above were incorporated into decorative laminating paper based on melamine resin and subsequently tested with regard to their optical properties and greying resistance in pressed laminates.
• the titanium dioxide pigment to be tested was incorporated into cellulose, and sheets with a sheet weight of roughly 100 g/m 2 and a TiO 2 content of about 40% by mass were produced.
• a 36.5% aqueous pigment suspension made of 146 g titanium dioxide pigment and 254 g tap water is prepared. Testing is based on 30 g pulp (oven-dry). The corresponding quantity of pigment suspension is adapted to the retention and the required ash content, 40 ⁇ 1% in this case, and the grammage, 100 ⁇ 1 g/m 2 in this case. A person skilled in the art is familiar with the procedure and the auxiliaries used.
• the ash content (titanium dioxide content) of a sheet and the retention of the pigment are subsequently determined.
• the ash content is determined by incinerating a defined weight of the produced paper in a rapid incinerator at 900° C.
• the TiO 2 content by mass can be calculated by weighing the residue.
• the retention is defined as the capacity to retain all inorganic substances in the sheet of paper on the wire screen of the paper-making machine.
• the “one-pass retention” indicates the percentage retained during a single feeding step to the paper-making machine.
• the ash content in percent referred to the percentage by mass of the pigment used relative to the total solids in the suspension yields the retention.
• the further processing of the paper encompasses its impregnation and pressing into laminates.
• the sheet to be impregnated with resin is immersed in a resin solution and pre-condensed for 25 seconds at 130° C. in a recirculating-air drying oven. Impregnation is performed a second time in similar manner, where the dwell time in the drying oven is 110 seconds.
• the sheet has a residual moisture content of 4 to 6% by weight.
• the condensed sheets are combined into stacks with phenolic resin-impregnated core papers, and white and black underlay paper.
• the laminate structure used for the test comprised 9 layers: decor sheet, decor sheet, core paper, core paper, black underlay, core paper, core paper, black/white underlay, decor sheet.
• the stacks are pressed for 300 seconds with the help of a Wickert Type 2742 laminating press at a temperature of 140° C. and a pressure of 90 bar.
• optical properties and the greying resistance of the laminates were measured using commercially available equipment (spectrophotometer, Xenotest weathering machine).
• the optical values (CIELAB L*, a*, b*) to DIN 6174 are measured with the help of the ELREPHO® 3000 calorimeter over white and black underlay.
• the opacity is a measure of the light transmission of the paper.
• the values are measured using a spectrophotometer (ELREPHO® 3000).
• the corresponding laminate samples are exposed in a XENOTEST® 150S.
• the side of the laminate on which two papers are laminated together is measured for the assessment.
• the CIELAB L*, a* and b* optical values to DIN 6174 are measured before and after 96 hours of exposure in the XENOTEST® 150S.
• the light source is a xenon-arc lamp.
• the temperature inside the device is 23 ⁇ 3° C., the relative humidity being 65 ⁇ 5%.
• the samples are rotated during the exposure cycle.
• test results for the laminates produced using the pigment according to the invention from the Example 1 and the pigments from Comparative examples 1 and 2 are summarised in Table I. All three examples and comparative examples are set to the same ash content.
• the laminate produced using the pigment according to the invention is characterised by both high opacity (L* black and L) and high greying resistance ( ⁇ L* and ⁇ E*).
• the laminates produced using the two reference pigments 1 and 2 display significantly lower values for either opacity (Comparative example 1) or greying resistance (Comparative example 2).
• the retention of the paper produced using the pigment according to the invention was improved relative to Comparative example 2.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Paper (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)

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• 2002
  • 2002-08-08 DE DE2002136366 patent/DE10236366A1/de not_active Ceased
• 2003
  • 2003-07-18 AU AU2003251000A patent/AU2003251000B2/en not_active Ceased
  • 2003-07-18 EP EP20030792215 patent/EP1603978B1/de not_active Expired - Lifetime
  • 2003-07-18 PL PL37338903A patent/PL373389A1/xx unknown
  • 2003-07-18 CA CA002493978A patent/CA2493978A1/en not_active Abandoned
  • 2003-07-18 BR BR0305745A patent/BR0305745A/pt not_active IP Right Cessation
  • 2003-07-18 AT AT03792215T patent/ATE550390T1/de active
  • 2003-07-18 MX MXPA05000973A patent/MXPA05000973A/es active IP Right Grant
  • 2003-07-18 CN CNB038173425A patent/CN1296439C/zh not_active Expired - Fee Related
  • 2003-07-18 JP JP2004530040A patent/JP4638733B2/ja not_active Expired - Fee Related
  • 2003-07-18 WO PCT/EP2003/007887 patent/WO2004018568A1/de active Application Filing
  • 2003-07-21 TW TW92119790A patent/TW200402452A/zh not_active IP Right Cessation
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